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A long-term historical emission inventory of air and climate pollutants in East, Southeast, and South Asia during 1950–2015 was developed as the Regional Emission inventory in ASia version 3 (REASv3). REASv3 provides details of emissions from major anthropogenic sources for each country and its sub-regions and also provides monthly gridded data with 0.25∘ × 0.25∘ resolution. The average total emissions in Asia during 1950–1955 and during 2010–2015 (growth rates in these 60 years estimated from the two averages) are as follows: SO2: 3.2 Tg, 42.4 Tg (13.1); NOx: 1.6 Tg, 47.3 Tg (29.1); CO: 56.1 Tg, 303 Tg (5.4); non-methane volatile organic compounds: 7.0 Tg, 57.8 Tg (8.3); NH3: 8.0 Tg, 31.3 Tg (3.9); CO2: 1.1 Pg, 18.6 Pg (16.5) (CO2 excluding biofuel combustion 0.3 Pg, 16.8 Pg (48.6)); PM10: 5.9 Tg, 30.2 Tg (5.1); PM2.5: 4.6 Tg, 21.3 Tg (4.6); black carbon: 0.69 Tg, 3.2 Tg (4.7); and organic carbon: 2.5 Tg, 6.6 Tg (2.7). Clearly, all the air pollutant emissions in Asia increased significantly during these 6 decades, but situations were different among countries and regions. Due to China's rapid economic growth in recent years, its relative contribution to emissions in Asia has been the largest. However, most pollutant species reached their peaks by 2015, and the growth rates of other species were found to be reduced or almost zero. On the other hand, air pollutant emissions from India showed an almost continuous increasing trend. As a result, the relative ratio of emissions of India to that of Asia has increased recently. The trend observed in Japan was different from the rest of Asia. In Japan, emissions increased rapidly during the 1950s–1970s, which reflected the economic situation of the period; however, most emissions decreased from their peak values, which were approximately 40 years ago, due to the introduction of control measures for air pollution. Similar features were found in the Republic of Korea and Taiwan. In the case of other Asian countries, air pollutant emissions generally showed an increase along with economic growth and motorization. Trends and spatial distribution of air pollutants in Asia are becoming complicated. Data sets of REASv3, including table of emissions by countries and sub-regions for major sectors and fuel types, and monthly gridded data with 0.25∘ × 0.25∘ resolution for major source categories are available through the following URL: https://www.nies.go.jp/REAS/index.html (last access: 31 October 2020).

This study presents the results of the ERTDF S-12 project for searching an optimum reduction scenario of the short-lived climate pollutants (SLCPs) to simultaneously mitigate the global warming and environmental problems. The study utilized REAS emission inventory, Asia-Pacific Integrated Model-Enduse (AIM/Enduse), MIROC6 climate model, NICAM non-hydrostatic atmospheric model, and models for estimating environmental damages to health, agriculture, and flood risks. Results of various scenario search indicate that it is difficult to attain simultaneous reduction of global warming and environmental damages, unless a significant reduction of CO2 is combined with carefully designed SLCP reductions for CH4, SO2, black carbon (BC), NOx, CO, and VOCs. In this scenario design, it is important to take into account the impact of small BC reduction to the surface air temperature and complex atmospheric chemical interactions such as negative feedback between CH4 and NOx reduction. We identified two scenarios, i.e., B2a and B1c scenarios which combine the 2D-scenario with SLCP mitigation measures using End-of-Pipe (EoP) and new mitigation technologies, as promising to simultaneously mitigate the temperature rise by about 0.33 °C by 2050 and air pollution in most of the globe for reducing damages in health, agriculture, and flood risk. In Asia and other heavy air pollution areas, health-care measures have to be enhanced in order to suppress the mortality increase due to high temperature in hot spot areas caused by a significant cut of particulate matter. For this situation, the B1b scenario is better to reduce hot spot areas and high-temperature damage to the public health.

A long-term historical emission inventory of air and climate pollutants in East, Southeast, and South Asia from 1950–2015 was developed as the Regional Emission inventory in ASia version 3.1 (REASv3.1). REASv3.1 provides details of emissions from major anthropogenic sources for each country and its sub-regions and also provides monthly gridded data with 0.25° × 0.25° resolution. The average total emissions in Asia during 1950–1955 and from 2010–2015 (growth rates in these 60 years) are as follows: SO2: 3.15 Tg, 42.4 Tg (13.5); NOx: 1.83 Tg, 47.6 Tg (26.0); CO: 62.2 Tg, 319 Tg (5.13); non-methane volatile organic compounds: 9.14 Tg, 61.8 Tg (6.77); NH3: 7.99 Tg, 31.3 Tg (3.92); CO2: 1.12 Pg, 18.3 Pg (16.3); PM10: 5.76 Tg, 28.4 Tg (4.92); PM2.5: 4.52 Tg, 20.3 Tg (4.50); black carbon: 0.751 Tg, 3.38 Tg (4.51); and organic carbon: 2.62 Tg, 6.92 Tg (2.64). Clearly, all the air pollutant emissions in Asia increased significantly during these six decades, but situations were different among countries and regions. Due to China's rapid economic growth in recent years, its relative contribution to emissions in Asia has been the largest. However, most pollutant species reached their peaks by 2015 and the growth rates of other species was found to be reduced or almost zero. On the other hand, air pollutant emissions from India showed an almost continuous increasing trend. As a result, the relative ratio of emissions of India to that of Asia have increased recently. The trend observed in Japan was different from the rest of Asia. In Japan, emissions increased rapidly during 1950s–1970s, which reflected the economic situation of the period; however, most emissions decreased from their peak values, which were approximately 40 years ago, due to the introduction of regulations and laws for air pollution. Similar features were found in the Republic of Korea and Taiwan. In the case of other Asian countries, air pollutant emissions generally showed an increase along with economic growth and motorization. Trends and spatial distribution of air pollutants in Asia are becoming complicated. Datasets of REASv3.1, including table of emissions by countries and sub-regions for major sectors and fuel types, and monthly gridded data with 0.25° × 0.25° resolution for major source categories are available through the following URL: http://www.nies.go.jp/REAS/.

The Fukushima Dai-ichi Nuclear Power Plant accidents following the March 11, 2011 Tohoku earthquake, and subsequent tsunami released radioactive materials into the atmosphere and caused significant public health concerns, particularly thyroid cancers in children. However, the lack of measurement data for atmospheric concentrations of

The urban model inter-comparison study (UMICS) was conducted in order to improve the performance of air quality models (AQMs) for simulating fine particulate matter (PM2.5) in the Greater Tokyo Area of Japan. UMICS consists of three phases: the first phase focusing on elemental carbon (UMICS1), the second phase focusing on sulfate, nitrate and ammonium (UMICS2), and the third phase focusing on organic aerosol (OA) (UMICS 3). In UMICS2/3, all the participating AQMs were the Community Multiscale Air Quality modeling system (CMAQ) with different configurations, and they similarly overestimated PM2.5 nitrate concentration and underestimated PM2.5 OA concentration. Various sensitivity analyses on CMAQ configurations, emissions and boundary concentrations, and meteorological fields were conducted in order to seek pathways for improvement of PM2.5 simulation. The sensitivity analyses revealed that PM2.5 nitrate concentration was highly sensitive to emissions of ammonia (NH3) and dry deposition of nitric acid (HNO3) and NH3, and PM2.5 OA concentration was highly sensitive to emissions of condensable organic compounds (COC). It was found that PM2.5 simulation was substantially improved by using modified monthly profile of NH3 emissions, larger dry deposition velocities of HNO3 and NH3, and additionally estimated COC emissions. Moreover, variability in PM2.5 simulation was estimated from the results of all the sensitivity analyses. The variabilities on CMAQ configurations, chemical inputs (emissions and boundary concentrations), and meteorological fields were 6.1-6.5, 9.7-10.9, and 10.3-12.3%, respectively.

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2018-01-25, 資料番号: PA1810047000

Chemical transport models are useful tools for evaluating source contributions and health impacts of PM2.5 in the atmosphere. We recently found that concentrations of PM2.5 compounds over Japan were much better reproduced by a volatility basis set model with an enhanced dry deposition velocity of HNO3 and NH3 compared with a two-product yield model. In this study, we evaluated the sensitivities to organic aerosol models of the simulated source contributions to PM2.5 concentrations and of PM2.5-related mortality. Overall, the simulated source contributions to PM2.5 were similar between the two models. However, because of the improvements associated with the volatility basis set model, the contributions of ammonia sources decreased, particularly in winter and spring, and contributions of biogenic and stationary evaporative sources increased in spring and summer. The improved model estimated that emission sources in Japan contributed 35%–48% of the PM2.5-related mortality in Japan. These values were higher t...

The MIX inventory is developed for the years 2008 and 2010 to support the Model Inter-Comparison Study for Asia (MICS-Asia) and the Task Force on Hemispheric Transport of Air Pollution (TF HTAP) by a mosaic of up-to-date regional emission inventories. Emissions are estimated for all major anthropogenic sources in 29 countries and regions in Asia. We conducted detailed comparisons of different regional emission inventories and incorporated the best available ones for each region into the mosaic inventory at a uniform spatial and temporal resolution. Emissions are aggregated to five anthropogenic sectors: power, industry, residential, transportation, and agriculture. We estimate the total Asian emissions of 10 species in 2010 as follows: 51.3 Tg SO2, 52.1 Tg NOx, 336.6 Tg CO, 67.0 Tg NMVOC (non-methane volatile organic compounds), 28.8 Tg NH3, 31.7 Tg PM10, 22.7 Tg PM2.5, 3.5 Tg BC, 8.3 Tg OC, and 17.3 Pg CO2. Emissions from China and India dominate the emissions of Asia for most of the species. We also estimated Asian emissions in 2006 using the same methodology of MIX. The relative change rates of Asian emissions for the period of 2006–2010 are estimated as follows: −8.1 % for SO2, +19.2 % for NOx, +3.9 % for CO, +15.5 % for NMVOC, +1.7 % for NH3, −3.4 % for PM10, −1.6 % for PM2.5, +5.5 % for BC, +1.8 % for OC, and +19.9 % for CO2. Model-ready speciated NMVOC emissions for SAPRC-99 and CB05 mechanisms were developed following a profile-assignment approach. Monthly gridded emissions at a spatial resolution of 0.25° × 0.25° are developed and can be accessed from http://www.meicmodel.org/dataset-mix.

The amount of 137Cs released by the Fukushima Dai-ichi Nuclear Power Plant accident of 11 March 2011 was inversely estimated by integrating an atmospheric dispersion model, an a priori source term, and map of deposition recorded by aircraft. An a posteriori source term refined finer (hourly) variations comparing with the a priori term, and estimated 137Cs released 11 March to 2 April to be 8.12 PBq. Although time series of the a posteriori source term was generally similar to those of the a priori source term, notable modifications were found in the periods when the a posteriori source term was well-constrained by the observations. Spatial pattern of 137Cs deposition with the a posteriori source term showed better agreement with the 137Cs deposition monitored by aircraft. The a posteriori source term increased 137Cs deposition in the Naka-dori region (the central part of Fukushima Prefecture) by 32.9%, and considerably improved the underestimated a priori 137Cs deposition. Observed values of deposition measured at 16 stations and surface atmospheric concentrations collected on a filter tape of suspended particulate matter were used for validation of the a posteriori results. A great improvement was found in surface atmospheric concentration on 15 March; the a posteriori source term reduced root mean square error, normalized mean error, and normalized mean bias by 13.4, 22.3, and 92.0% for the hourly values, respectively. However, limited improvements were observed in some periods and areas due to the difficulty in simulating accurate wind fields and the lack of the observational constraints.

For the source apportionment of carbonaceous aerosols, measurement of 14 C is an effective technique. In particular, diurnal variations of fossil and nonfossil carbonaceous aerosols provide information about the sources and production pathways of elemental carbon (EC) and organic carbon (OC). In this study, concentrations of fine-mode aerosols, including EC, OC, and 14 C, were observed with a time resolution of 6 h near the urban center of Beijing in June 2010. The observations indicate that the contribution of fossil secondary organic aerosol (SOA) increased during daytime. This finding is consistent with previous studies in other urban sites, suggesting that SOA production from anthropogenic sources is important in urban areas. We evaluated the performance of two chemical transport models (CTMs) with different SOA models on simulations of EC and OC. Both models well reproduced the concentration and diurnal variation of EC. OC concentrations were underestimated by more than half by the CTM with a SOA yield model, and were better reproduced by the CTM with a volatility basis set (VBS) model. However, even the VBS model underestimated both fossil and nonfossil total carbon (EC + OC), and possible reasons for this underestimation are discussed.

Air pollutants such as tropospheric ozone and PM2.5 travel through large areas. The damage factors (DFs) presented by existing researches in life cycle impact assessment do not take into consideration transboundary movement. A previous study used a global chemistry transport model (CTM), to develop health damage factors for ten different regions around the world by considering the transboundary movement of PM2.5. Under the same assessment procedure, this research is designed to calculate the ozone DFs by region and to find the effects of wide range movement on the DFs. The DFs by regions are defined as changes in disability-adjusted life years (DALYs) derived from changes in tropospheric ozone concentration around the world which is induced by an increase in emissions of the unit amount of nitrogen oxides (NOx) and non-methane volatile organic compounds (NMVOC). DFs for ten regions are calculated as follows. Firstly, the concentration change of worldwide ozone caused by a change in emission of a substance from one region is estimated with a global scale CTM for both NOx and NMVOC. Secondly, DALY changes on the world due to a change in concentration of ozone are estimated by using population data and epidemiological concentration-response functions for mortality and morbidity. Finally, the above calculations are done for all targeted ten regions. DFs of NOx and NMVOC for ten regions were calculated as 0.3–4.2 × 10−5 DALY/kg and 0.2–5.6 × 10−6 DALY/kg, respectively. It was found DFs might be underestimated around 10 to 70 % by region if the transboundary movement is not taken into consideration. In many regions in the northern hemisphere, about 60 % of damage occurs outside the emission area, which is larger than that of southern hemispheric regions due to a larger population exposed to downwind places. In regions of China and India, however, the influence on other regions accounted for only 10 % because these regions involve larger influences in the source region. The impact of NO titration effect can be seen in cold seasons in many regions, but it was found that the effect is remarkable on an annual average only in Europe, a cold region with large emissions. The human health DFs of NOx and NMVOC considering effects of transboundary movement of tropospheric ozone are estimated for ten regions by using a global CTM. As a future work, it is important to show the interannual sensitivity of the DFs through chronological assessments.

The Fukushima Dai-ichi Nuclear Power Plant accidents following the March 11, 2011 Tohoku earthquake, and subsequent tsunami released radioactive materials into the atmosphere and caused significant public health concerns, particularly thyroid cancers in children. However, the lack of measurement data for atmospheric concentrations of 131I has caused persistent and widespread uncertainty. This study estimated the maximum potential thyroid doses of inhaled 131I in the early post-accident phase between March 12 and 23, 2011 by using the hourly measured data of the 137Cs concentrations at 101 suspended particulate matter (SPM) monitoring sites, a new multi-model ensemble (MME) method of simulating 137Cs concentrations using two Atmospheric Transport and Deposition Models (ATDMs), the 131I/137Cs ratio obtained from measurement data analysis, and the internal exposure model. Based on the measurements, the maximum potential thyroid doses were estimated at 3.1–160 mSv at 5 sites in the Fukushima-Hamadori area for 1-year-old children assumed to remain outdoors, whereas they were less than 4.3 mSv at the other sites in the base case of the 131I/137Cs ratio. The spatial distribution of the maximum potential of early inhalation doses was estimated by using the MME and measurements. The inhalation thyroid doses in the evacuation scenarios were compared to the estimates reported by previous studies. The results of the present study were almost congruent with the outcomes of previous investigations except for thyroid doses contributed by highly contaminated plumes on March 12 and 15. The sensitivity analysis for the 131I/137Cs ratio indicated that these plumes carried the potential to significantly increase the thyroid doses of residents.

Massive amounts of anthropogenic radiocaesium 137Cs that was released into the environment by the Fukushima Dai-ichi Nuclear Power Plant accident on March 2011 are widely known to have extensively migrated to Pacific oceanic sediment off of east Japan. Several recent reports have stated that the sedimentary 137Cs is now stable with a remarkably heterogeneous distribution. The present study elucidates ocean dynamic processes causing this heterogeneous sedimentary 137Cs distribution in and around the shelf off Fukushima and adjacent prefectures. We performed a numerical simulation of oceanic 137Cs behaviour for about 10 months after the accident, using a comprehensive dynamic model involving advection–diffusion transport in seawater, adsorption and desorption to and from particulate matter, sedimentation and suspension on and from the bottom, and vertical diffusion transport in the sediment. A notable simulated result was that the sedimentary 137Cs significantly accumulated in a swath just offshore of the shelf break (along the 50–100 m isobath) as in recent observations, although the seabed in the entire simulation domain was assumed to have ideal properties such as identical bulk density, uniform porosity, and aggregation of particles with a single grain diameter. This result indicated that the heterogeneous sedimentary 137Cs distribution was not necessarily a result of the spatial distribution of 137Cs sediment adsorptivity. The present simulation suggests that the shape of the swath is mainly associated with spatiotemporal variation between bottom shear stress in the shallow shelf (< 50 m depths) and that offshore of the shelf break. In a large part of the shallow shelf, the simulation indicated that strong bottom friction suspending particulate matter from the seabed frequently occurred via a periodic spring tide about every 2 weeks and via occasional strong wind. The sedimentary 137Cs thereby could hardly stay on the surface of the seabed with the result that the simulated sediment-surface 137Cs activity tended to decrease steadily for a long term after the initial 137Cs migration. By contrast, in the offshore region, neither the spring tide nor the strong wind caused bottom disturbance. Hence, the particulate matter incorporated with 137Cs, which was horizontally transported from the adjacent shallow shelf, readily settled and remained on the surface of the sediment just offshore of the shelf break. The present simulation also clearly demonstrated that the bottom disturbance influenced the sedimentary 137Cs distributions not only horizontally but also vertically. In particular, within a part of the near-shore off the nuclear power plant, the simulation indicated that large amounts of the sedimentary 137Cs were present in both upper and deeper sediments. As a result, total sedimentary 137Cs in the entire simulation domain (1.4 x 105 km2) at the end of 2011 was 3.2 x 1015 Bq, more than 10 times that in previous estimates using samples of upper sediments.

Bottom-up emission inventories can provide valuable information for understanding emission status and are needed as input datasets to drive chemical transport models. However, this type of inventory has the disadvantage of taking several years to be compiled because it relies on a statistical dataset. Top-down approaches use satellite data as a constraint and overcome this disadvantage. We have developed an immediate inversion system to estimate anthropogenic NO x emissions with NO2 column density constrained by satellite observations. The proposed method allows quick emission updates and considers model and observation errors by applying linear unbiased optimum estimations. We used this inversion system to estimate the variation of anthropogenic NO x emissions from China and India from 2005 to 2016. On the one hand, NO x emissions from China increased, reaching a peak in 2011 with 29.5 Tg yr−1, and subsequently decreased to 25.2 Tg yr−1 in 2016. On the other hand, NO x emissions from India showed a continuous increase from 2005 to 2016, reaching 13.9 Tg yr−1 in 2016. These opposing trends from 2011 to 2016 were −0.83 and +0.76 Tg yr−1 over China and India, respectively, and correspond to strictly regulated and unregulated future scenarios. Assuming these trends continue after 2016, we expect NO x emissions from China and India will be similar in 2023, with India becoming the world’s largest NO x emissions source in 2024.

International audience; Since the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in March 2011, atmospheric simulation models have improved our understanding of the atmospheric behavior of radionuclides. Model intercomparisons provide valuable and useful information for evaluating the validity and variability of individual model results. In this study, we compared results of seven atmospheric transport models used to simulate 137Cs released from the FDNPP to the atmosphere. All model results used in this analysis had been submitted for a model intercomparison project of the Science Council of Japan (2014, http//www.scj.go.jp/en/report/index.html). Here we assessed model performance by comparing model results with observed hourly atmospheric concentrations of 137Cs, with a particular focus on nine plumes over the Tohoku and Kanto regions. The intercomparison results showed that model performance in reproducing 137Cs concentrations was highly variable among different models and plumes. In general, models better reproduced plumes that passed over many observation stations. The performance among the models was consistent with the simulated wind fields and the source terms used. We also assessed model performance in relation to accumulated 137Cs deposition. Simulated areas of high 137Cs deposition were consistent with the simulated 137Cs plume pathways, though the models that best simulated atmospheric 137Cs concentrations were different from those that best simulated deposition. The ensemble mean of all models consistently reproduced atmospheric 137Cs concentrations and deposition well, suggesting that use of a multimodel ensemble results in more effective and consistent model performance. ©2018. American Geophysical Union. All Rights Reserved.

The behavior of tropospheric NO2 vertical column density (VCD) over continental Southeast Asia (Cambodia, Laos, Myanmar, Thailand, and Vietnam) was systematically analyzed using observations from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) and a regional chemical transport model (CTM) during 2003–2008. NO2 VCD over continental Southeast Asia showed a distinctive large peak from winter (December) to early spring (April). The regional CTM was configured with anthropogenic emissions taken from the Regional Emission inventory in Asia (REAS) version 2.1 and biomass burning emissions taken from the Global Fire Emissions Database (GFED) version 3.1. Overall, the model could reproduce the NO2 VCD observed by space-borne sensors. A mismatch between satellite observations and the regional CTM was found only in January over Cambodia. A likely reason for this mismatch was diurnal variation in biomass burning emissions. During the analysis period, the largest biomass burning event was reported from December 2003 to April 2004, and a sensitivity analysis was conducted by omitting the biomass burning emissions in the CTM. It was found that the seasonal variations of NO2 VCD, with the peak during winter to early spring, were caused by biomass burning emissions in all countries in continental Southeast Asia. The contribution of biomass burning emissions to NO2 VCD over continental Southeast Asia was an average of 28% during this period and a maximum of 58% in March 2004.

This chapter provides an analysis of the urban pollution and potential for co-benefits in India, making a comparison with other South Asian countries. Most of the South Asian countries are at the stage of developing or emerging economies, and India is the fastest growing economy among them. The Indian subcontinent is comprised of hundreds of densely populated large and medium size cities including five megacities (each with a population of more than 10 million). Constantly increasing energy-intensive urban activities in burgeoning cities and biomass burning in rural areas of India are responsible for a large share in the unacceptably high emissions of health-endangering and environment-polluting gaseous and particulate pollutants. The air pollution problem in India and the rest of the South Asia came into the spotlight by the South Asian haze called the Atmospheric Brown Cloud (ABC), which is said to be responsible for annually 100,000s premature deaths in the South Asian region (Lelieveld et al. 2001). Given the increasing trend of energy use and emissions in Indian cities, the present study is a step to make governments and people aware of the extent and intensity of the ambient as well as the indoor air pollution problem. The analysis presented in this study is expected to help initiate appropriate policy measures and suitable action plans to limit emissions and adopt ways based on the co-benefits approach that promote sustainable development.

A better understanding of land cover/land use changes (LCLUC) and their interactions with the atmospheric environment is essential for the sustainable management of natural resources, environmental protection, air quality, agricultural planning and food security. The 15 papers published in this focus issue showcase a variety of studies relating to drivers and impacts of LCLUC and air pollution in different South/Southeast Asian (S/SEA) countries. This synthesis article, in addition to giving context to the articles in this focus issue, also reviews the broad linkages between population, LCLUC and air pollution. Additionally, we identify knowledge gaps and research priorities that are essential in addressing air pollution issues in the region. We conclude that for effective pollution mitigation in S/SEA countries, quantifying drivers, sources and impacts of pollution need a thorough data analysis through ground-based instrumentation, models and integrated research approaches. We also stress the need for the development of sustainable technologies and strengthening the scientific and resource management communities through capacity building and training activities to address air pollution issues in S/SEA countries.

Chemical transport models are useful tools for evaluating source contributions and health impacts of PM

Sulfate aerosols simulated by an aerosol module coupled to the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) at a spatial resolution (220 km) widely used by global climate models were evaluated by a comparison with in situ observations and the same aerosol module coupled to the Model for Interdisciplinary Research on Climate (MIROC) over East Asia for January, April, July, and October 2006. The results indicated that a horizontal gradient of sulfate from the source over China to the outflow over Korea-Japan was present in both the simulations and the observations. At the observation sites, the correlation coefficients of the sulfate concentrations between the simulations and the observations were high (NICAM: 0.49–0.89, MIROC: 0.61–0.77), whereas the simulated sulfate concentrations were lower than those obtained by the observation with the normalized mean bias of NICAM being −68 to −54% (all), −77 to −63% (source), and −67 to −30% (outflow) and that of MIROC being −61 to −28% (all), −77 to −63% (source), and −60 to +2% (outflow). Both NICAM and MIROC strongly underpredict surface SO2 over China source regions and Korea-Japan outflow regions, but the MIROC SO2 is much higher than NICAM SO2 over both regions. These differences between the models were mainly explained by differences in the sulfate formation within clouds and the dry deposition of SO2. These results indicated that the uncertainty of the meteorological and cloud fields as well as the vertical transport patterns between the different host climate models has a substantial impact on the simulated sulfate distribution.

An aerosol-coupled global nonhydrostatic model with a stretched-grid system has been developed. Circulations over the global and target domains are simulated with a single model, which includes fine meshes covering the target region to calculate meso-scale circulations. The stretched global model involves lower computational costs to simulate atmospheric aerosols with fine horizontal resolutions compared with a global uniform nonhydrostatic model, whereas it may require higher computational costs compared with the general regional models, because the stretched-grid system calculates inside and outside the target domain. As opposed to general regional models, the stretched-grid system requires neither a nesting technique nor lateral boundary conditions. In this study, we developed a new-type regional model for the simulation of aerosols over Japan, especially in the Kanto areas surrounding Tokyo, with a maximum horizontal resolution of approximately 10 km. This model usually reproduces temporal variations and their averages of the observed weather around Japan. This model generally reproduces monthly mean distributions of the observed sulfate and SO2 over East Asia, with high correlations (R > 0.6), but the underestimation of the simulated concentrations by 40% (sulfate) and 50% (SO2). Their underestimation of the simulated sulfate and SO2 concentrations over East Asia are strongly affected by their underestimation in China and possibly by the uncertainty of the simulated precipitation around Japan. In the Kanto area, this model succeeds in simulating the wind patterns and the diurnal transitions around the center of the Kanto area, although it is inadequate to simulate the wind patterns and the diurnal transitions at some sites located at the edge of the Kanto area and surrounded on three sides by mountains, e.g., Maebashi, mainly due to the insufficient horizontal resolution. This model also generally reproduces both diurnal and synoptic variations of the observed and/or a regional aerosol-transport model, WRF-CMAQ, simulated EC, sulfate, and SO2 concentrations in the Kanto area, especially with their high correlation (R > 0.5) at Komae/Tokyo. Although the aerosol module used in this study is relatively simplified compared to the general regional aerosol models, this study reveals that our proposed model with the stretched-grid system can be applicable for the regional aerosol simulation.

Purpose Health damage from ambient fine particulate matter (PM2.5) shows large regional variations and can have an impact on a global scale due to its transboundary movement. However, existing damage factors (DFs) for human health in life cycle assessments (LCA) are calculated only for a few limited regions based on various regional chemical transport models (CTMs). The aim of this research is to estimate the human health DFs of PM2.5 originating from ten different regions of the world by using one global CTM.

Objective: This study clarified sensitization patterns to house dust mite (HDM) and Japanese cedar pollen (JCP) in Japanese lower-grade schoolchildren. We also explored factors associated with allergic sensitization. Methods: This cross-sectional study used a database from the Study on Respiratory Disease and Automobile Exhaust (SORA), a Japanese health study project. The subjects comprised 8,815 pupils aged 6-9 years. We obtained the distribution of HDM- and JCP-specific IgE, respectively, as a marker of sensitization. To determine factors associated with sensitization, we used logistic regression and calculated adjusted odds ratios (AORs) for the relative prevalence of sensitization. The cut-off point for specific IgE levels was 0.35 kU/l. Results: Sensitization to HDM and JCP was detected in 51 and 39% of subjects, respectively, occurring more often in boys and at older ages. In addition, AORs of sensitization to HDM/JCP were higher in subjects with a history of bronchitis, parental asthma, parental atopic eczema and parental pollinosis. In contrast, AORs for sensitization were lower in those subjected to maternal passive smoking as well as among boys with pets. AORs of sensitization to JCP alone were lower in those with a history of otitis media, those who had been bottle milk fed, and those who were not the firstborn and who lived near a busy road. Conclusion: Sensitization to HDM and JCP was detected in 51 and 39% of lower-grade schoolchildren, respectively.

Evaluation of models for simulating temporal and spatial variations of PM2.5 chemical composition in Japan has been limited by the lack of observational data. In this study, we used PM2.5 chemical composition data measured simultaneously over several regions of Japan in winter, spring, and summer 2012 to evaluate three sensitivity simulations, one based on a secondary organic aerosol (SOA) yield model and two based on a volatility basis set (VBS) model. Concentrations of sulfate (SO42–), nitrate (NO3–), and ammonium (NH4+) were well reproduced by all the simulations in summer. However, in winter and spring, SO42– concentrations were underestimated and NO3– concentrations were overestimated by the standard simulation. NO3– concentrations were better reproduced by a model with dry-deposition velocities of nitric acid and ammonia enhanced by a factor of 5, as was done in a previous study. Observed concentrations of elemental carbon and organic aerosol (OA) were higher at urban sites than at the surrounding remote sites, and this behavior was not adequately reproduced by models with a grid size of 15 km. Further refinements of emission inventories and models are necessary for better simulations of PM2.5 chemical compositions. OA concentration was greatly underestimated by the simulation based on the SOA yield model over all the seasons but was better reproduced by the simulations based on the VBS model in spring and summer because aging reactions were considered in the VBS model-based simulations. The VBS model-based simulations reproduced the observations that primary OA predominated in winter and that the contribution of SOA was higher than that of primary OA in spring and summer. These contributions should be validated by means of observation-based source contributions of OA in future studies.

We conducted continuous measurements of NOy and total nitrate (T.NO3 = HNO3 + NO 3 − ( p ) ) at Fukue Island, Nagasaki, and Cape Hedo, Okinawa, Japan. We compared variations of NOy or T.NO3 concentrations measured at two remote sites when the air masses were originated from the same regions of the Asian Continent. Long-range transport events from the Asian Continent were extracted by CO concentration peaks at Fukue and Hedo and backward trajectory analyses. We compared the transport time difference at two sites from the Asian continent with the ratios of NOy at Hedo to that at Fukue (=R(NOy)) to find the predominant factor in NOy removal. R(NOy) were less than unity and decreased with the transport time difference. The ratios of NOy/CO at Hedo to those at Fukue (R(NOy/CO)) was assumed to be affected by the deposition process. R(NOy/CO) showed negative correlation with transport time difference as the same the case of R(NOy). This indicates that NOy was mainly removed by deposition rather than dilution. Air mass ages were classified by the ratio of T.NO3 to NOy at Fukue: T.NO3/NOy

This study determined the production-based emissions, the consumption-based emissions, and the consumption-based health impact of primary carbonaceous aerosols (black carbon: BC, organic carbon: OC) in nine countries and regions in Asia (Indonesia, Malaysia, the Philippines, Singapore, Thailand, China, Taiwan, South Korea, and Japan) in 2008. For the production-based emissions, sectoral emissions inventory of BC and OC for the year of 2008 based on the Asian international input–output tables (AIIOT) was compiled including direct emissions from households. Then, a multiregional environmental input–output analysis with the 2008 AIIOT which was originally developed by updating the table of 2000 was applied for calculating the consumption-based emissions for each country and region. For the production-based emissions, China had the highest BC and OC emissions of 4520 Gg-C in total, which accounted for 75% of the total emissions in the nine countries and regions. For consumption-based emissions, China was estimated to have had a total of 4849 Gg-C of BC and OC emissions, which accounted for 77% of the total emissions in the Asia studied. We also quantified how much countries and regions induced emissions in other countries and regions. Furthermore, taking account of the source–receptor relationships of BC and OC among the countries and regions, we converted their consumption-based emissions into the consumption-based health impact of each country and region. China showed the highest consumption-based health impact of BC and OC totaling 111 × 103 premature deaths, followed by Indonesia, Japan, Thailand and South Korea. China accounted for 87% of the sum total of the consumption-based health impacts of the countries/regions, indicating that China's contribution to consumption-based health impact in Asia was greater than its consumption-based emissions. By elucidating the health impacts that each country and region had on other countries and from which country the impacts were received, we demonstrated that the characteristics of the consumption-based health impact varied significantly by country and region. We also determined the difference in the health impacts to other countries and regions due to the domestic final demand of each country and region, and the health impact due to the domestic final demand of that country or region.

The relative contributions of various source regions to the long-term (1980–2005) increasing trend in surface ozone (O3) over Japan were estimated by a series of tracer-tagging simulations using a global chemical transport model. The model well simulated the observed increasing trend of surface O3 including its seasonal variation and geographical features in Japan and demonstrated the relative roles of different source regions in forming this trend. Most of the simulated increasing trend of surface O3 over Japan (~ 97 %) was explained as the sum of trends in contributions of different regions to photochemical O3 production. The increasing trend in O3 produced in China accounted for 36 % of the total increasing trend and those in the other northeast Asian regions (the Korean Peninsula, coastal regions in East Asia, and Japan) each accounted for about 12–15 %. Furthermore, the contributions of O3 created in the entire free troposphere and in West, South, and Southeast Asian regions also increased; and their increasing trends accounted for 16 and 7 % of the total trend, respectively. The impact of interannual variations in climate, in methane concentration, and in emission of O3 precursors from different source regions on the relative contributions of O3 created in each region estimated above was also investigated. The variation of climate and the increase in methane concentration together caused the increase of photochemical O3 production in several regions, and represented about 19 % of the total increasing trend of surface O3 over Japan. The increase in emission of O3 precursors in China caused an increase of photochemical O3 production not only in China itself but also in the other northeast Asian regions and accounted for about 46 % of the total increase in surface O3 over Japan. Similarly, the relative impact of O3 precursor emission changes in the Korean Peninsula and Japan were estimated as about 16 and 4 % of the total increasing trend, respectively. The O3 precursor emission change in regions other than northeast Asia caused increases in surface O3 over Japan mainly through increasing photochemical O3 production in West, South, and Southeast Asia and the free troposphere, and accounted for about 16 % of the total.

Sensitivity maps of atmospheric acid deposition in Japan have not been updated in 20 years. Here, we propose new relative risk maps of surface water acidification in forests based on a weighted overlay of cumulative potential acid deposition (CPAD) simulated for a 25-year period (1981–2005), including the sensitivities of soil and bedrock to acidification. We assumed that relative acidification risk is high in areas that exhibit high sensitivities of soil and bedrock to acid and have received a large amount of cumulative acid deposition over the past several decades. We aggregated fine soil and bedrock maps into a 20-km mesh for overlay onto an 80-km mesh map of CPAD by considering their spatial structures in Japan. Allocation of the weights among CPAD and soil and bedrock sensitivities was performed based on observational trends in river pH over the past 30 years. The resulting risk map for surface water acidification showed that large areas of western Japan, as well as smaller areas of Hokkaido, Tohoku, Kanto, and Kyushu, are at high risk of surface water acidification. Seventy-seven percent of all rivers for which a declining trend in pH was observed from 2001 to 2009 were also high-risk areas. Acid deposition might be one factor controlling surface water acidification in areas with high bedrock sensitivity, in addition to high CPAD and soil sensitivity, although the risk of soil acidification remains unclear.